1. Field of the Invention
The present invention relates to a transmission control system for controlling data transmission in radio packet communication, and more particularly, relates to a transmission control system for rendering acknowledgment in the data transmission by the use of one-to-multiple site communication.
2. Description of the Related Art
In one-to-multiple site communication on a network having the structure of an ad hoc network which is not connected to a fixed network, like a radio LAN or the like, acknowledgment processing is performed in order to surely confirm the acceptance of the data in every link. Such acknowledgment processing is performed in the same way as that in the one-to-one communication. On the contrary, the acknowledgment processing is not generally performed in the one-to-multiple site communication by the use of satellite communication, because it is inefficient to get the acknowledgment from all communication terminals and it is not practical to do so from the viewpoint of the reliability of the acknowledgment itself.
However, if the acknowledgment processing is not performed, reliability of signal transmission is extremely decreased. Therefore, proposed is a means for blocking the data to confirm the acceptance of the data for the purpose of increasing the reliability in the signal transmission. As this kind of technique, there is a technique, for example, described in the article "A Broadcast Protocol for File Transfers to Multiple Site", IEEE Trans. Commun., Vol. COM-29, No. 11, pp. 1701-1707, November 1981 written by Calo, S. B. et al.
However, in the above conventional technique of blocking the data to do acknowledgment, as the data size of one block becomes larger, each communication terminal must have a buffer of larger volume according to the size of the block, which results in increasing the cost of hardware disadvantageously. Further, increase in the procedure accompanied by the blocking of the data causes a defect such as to complicate the processing.
Also, a means for notifying not only the acknowledgment but also negative acknowledgment to confirm the acceptance is proposed in order to prevent from decreasing efficiency. As this kind of technique, there is a technique, for example, disclosed in Japanese Patent Publication Laid-Open (Kokai) No. Heisei 60-35851 "Communication System". In the same publication, a method is disclosed, in which when a receiving terminal couldn't receive a packet signal correctly, a negative acknowledgment signal (hereinafter, referred to as a NAK signal) is transmitted to collide with an acknowledgment signal (hereinafter, referred to as an Ack signal) or the NAK signal sent by a specified receiving terminal, thereby recognizing the failure of the data transmission, and retry is requested of the sending terminal.
However, the above conventional technique also has such a defect that it takes a lot of time to detect the Ack signal/the NAK signal, or detect the collision between the NAK signal and the Ack signal, indifferently to whether or not the Ack signal or NAK signal can be received correctly.
As mentioned above, in the conventional one-to-multiple site communication by the use of a satellite, the acknowledgment is not performed generally, thereby to reduce the reliability of the signal transmission.
When the acknowledgment is performed by blocking the data, it has such a defect as to increase the cost of the hardware according to the increase in the buffer capacity as well as to complicate the procedure accompanied by the blocking of the data.
Further, when the no-acceptance is confirmed by sending the negative acknowledgment signal, it takes a lot of time to recognize the failure of the data transmission, which results in preventing from the prompt response.